This invention relates to pliers with jaw spacing and load measuring readings, including a method of applying forces, and, more particularly, it relates to an instrument having jaws for gripping a workpiece and for measuring the gripping distance between the jaws and for measuring the force applied to the workpiece.
The prior art is already aware of instruments, like pliers-type instruments with pivotal handles and jaws, for manipulating a workpiece. Those instruments also include means for detecting the amount of pivoting between the handles when the jaws are in contact with the workpiece, and the instruments can detect the distance between the gripping locations on the workpiece. That can be a caliper-type instrument. The prior art also has arrangements of instrument handles which are resilient, or which have a resilient portion or addition, all for applying a force on the jaws through the resilient portion.
The present invention improves upon the prior art by providing an instrument with jaws and pivotal handles wherein the amount of handle pivot, when in contact with the work piece, can be read, and thus the distance between the contacts on the workpiece, and the amount of the forces applied to the workpiece, can be measured. With the detection of the applied forces, only continuous squeezing of the handles is required to produce the application of the desired forces, and this instrument will reveal the amount of those forces at various and selected stage, of force application.
This instrument is capable of applying and measuring various forces and not just one force which is applied by the fixed structural nature of the prior art instruments. In the use of this instrument in medical practice, such as in spine manipulation where force and measurement on vertebrae are required, this instrument will reveal the dimension on the spine and also the forces being applied to the spine. This all occurs with the need of only one gripping position on the handles and with the need of only continuous squeezing or pivoting of those handles.
The indicator, markers, scales, and pointers, whichever are employed, are arranged to be visible, and thus readable, from one viewing location or perspective, so the user need not strain nor move to read all the measurements. The user""s grip on the handles need not be released nor even moved from its normal squeezing location on the handles in order to view the readings.
Also, the aforementioned is accomplished with an instrument which can have parallel action jaws and which can be arranged for either compression or distraction action on the workpiece. The distraction can be employed on the spine for moving the vertebrae apart while applying only a specific and accurate distraction force of separation, and while the instrument displays the measurement of the changing distraction forces. With that arrangement, the readings are accurate because the length of the torque arm on each of the jaws is always constant, regardless of the location of the contact of the jaws with the workpiece, and the parallel linkage assembly provides for, and does not alter, that constant torque arm length. That constancy also pertains to the method.
Throughout, the instrument can have a spring for urging the handles apart and against the squeezing forces being applied, and it can have a threaded member for threadedly actuating the handles relative to each other to squeeze the handles for establishing the pivot action of the handles and securing them and the jaws at any selected pivoted position. Further, there is provision for restricting the pointer indicator for aligning it at a zero setting and thereby automatically achieving desired calibration of the instrument before using it.
A parallel linkage assembly is employed to achieve consistent readings by avoiding a torquing action applied to the workpiece by the pivoting handles. That is, the leverage of the pivoting is not effective beyond a set location on the instrument, and that is the location where parallel linkage may be connected in the instrument.